Abstract

Theoretical expressions for the modulation depth of moiré
signals under incoherent illumination are derived. Consequently,
the modulation depth of a moiré signal is related to the
following factors: the geometric shape and the size of the light
source; the diffraction effect of the grating, which relates to the
number of lines in the grating; the line and the space ratio; the
grating pair gap; the geometric shape and the size of the receiving
window; etc. In addition, the influence of the grating pair on the
period and the inclination of moiré fringes under noncollimated
illumination are discussed, and the changes in the moiré signal
modulation depth under noncollimated illumination with that under
collimated illumination are made. Finally, some experimental
results are given to verify the theoretical expressions. This
research is useful for the actual design of grating sensors.

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